Move Mbed TLS self tests to a separate configuration ...

We potentially save flash space by not enabling Mbed TLS self-tests
by default. A new test config file, TESTS/configs/mbedtls.json, is
provided to enable self tests. This newly created JSON file also
enables timing in Mbed TLS so timing gets tested.

mbedtls: Run mbedtls_timing_self_test if MBEDTLS_TIMING_C ...

This allows us to verify the support for Mbed TLS timing on Mbed OS.

Note: The macros MBEDTLS_TIMING_C and MBEDTLS_TIMING_ALT are not
enabled by default and need to be additionally enabled to run this
test.

mbedtls: Use LowPowerTimeout for mbedtls_set_alarm() if available ...

The function `mbedtls_set_alarm()` is only precise to seconds, so
`LowPowerTimeout` is enough and saves power.

timing_mbed.cpp: Check MBEDTLS_TIMING_ALT ...

Do not compile the Mbed implementation of Mbed TLS unless
MBEDTLS_TIMING_ALT is defined. This prevents a macro check error on
devices that do not have LPTICKER or USTICKER when Mbed TLS timing
is not enabled.

mbedtls: Add full platform implementation of timing ...

When MBEDTLS_TIMING_C and MBEDTLS_TIMING_ALT are enabled,
the Arm Compiler generates errors like the following (one for
each missing symbol):

    Error: L6218E: Undefined symbol mbedtls_timing_get_delay

Reason:

The function `mbedtls_timing_self_test()` in the Mbed TLS default
`timing.c` always gets compiled, if MBEDTLS_SELF_TEST is defined.
And MBEDTLS_SELF_TEST is always defined, as we have a Greentea test
to run some of the Mbed TLS self tests. (In the future we should try
not to enable MBEDTLS_SELF_TEST except for tests, but it requires
a rework in our test flow.)

`mbedtls_timing_self_test()` tests (calls) the full API declared in
`timing.h`, and the ARM Compiler requires all symbols referenced by
all functions to be defined, even those not used by the final
application. This is unlike GCC_ARM which resolves what are required.

Solution:

To fix the "undefined symbol" errors, we add an implementation of
`mbedtls_timing_get_timer()` based on Mbed OS `LowPowerTimer` or
`Timer` (depending on which one is available), and copy Mbed TLS's
default `mbedtls_timing_set_delay()` and `mbedtls_timing_get_delay()`
which are built on top of `mbedtls_timing_get_timer()`. This will also
benefit user applications that need to enable timing in Mbed TLS.

mbedtls: Use LowPowerTimer/Timer for timing ...

Previously we used `gettimeofday()` for Mbed TLS timing, but its
implementation provided by Mbed OS is only precise to seconds. The
microsecond component of the output `struct timeval` is always set
to zero. But Mbed TLS requires millisecond precision.

To provide required timing precision, switch to use `LowPowerTicker`
or (microsecond) `Ticker`. `LowPowerTicker` is preferred as it saves
power and Mbed TLS does not require microsecond precision.

Merge pull request #14750 from tymoteuszblochmobica/size_spi ...

Increase SPI stack size to 2048 for BlueNrg driver

Merge pull request #14765 from rwalton-arm/fix_unittest_check ...

Fix unittest check

Merge pull request #14748 from AlbanJeantheau-silabs/fix_calculate_ufsi ...

Correct ufsi timing calculation

Merge pull request #14743 from OpenNuvoton/nuvoton_m251_m261_wdt ...

Nuvoton: Support watchdog on M251/M261 series

Merge pull request #14734 from jeromecoutant/PR_RFSWITCH ...

STM32WL LORA: HW specific out of STM32WL_LoRaRadio class

Merge pull request #14760 from Patater/tls-timing-alt-fix ...

mbedtls: Rename Mbed timing implementation

Merge pull request #14737 from paul-szczepanek-arm/cmake-ble-rebased ...

BLE: Add cmake unittest fakes for BLE and events

remove unittest readme

Handle timer rollover in calculate_ufsi ...

Co-authored-by: Jarkko Paso <jarkko.paso@arm.com>

coding style

CMake: Only build unit tests if Mbed OS is the current project ...

Typically when adding a unit test directory to a CMake project a check
will be used to ensure the subdirectory is added only if the following
are true:

* The BUILD_TESTING option is set to ON.
* The current CMake project is the top-level project.

The reason being, if a downstream project includes our project they
generally don't want to build our unit tests.

In mbed-os, we do correctly specify the above condition before adding
the central UNITTEST subdirectory, which fetches googletest and adds the
"stub" libraries the unit tests depend on. However, we only check if
CMAKE_CROSSCOMPILING is OFF (or undefined) before actually adding the
unit tests. This mismatched logic would lead to unexpected build
failures in various scenarios. One likely case could be: a downstream
project including mbed-os happens to set CMAKE_CROSSCOMPILING to
OFF/undefined for any reason (possibly to build its own unit tests).
mbed-os would go ahead and attempt to build its tests without fetching
googletest or adding the required stub targets.

To fix the issue replace the check for CMAKE_CROSSCOMPILING in the unit
tests with the same BUILD_TESTING idiom we use for adding the central
UNITTESTS subdirectory.

CMake: unit-tests: Fetch googletest master ...

googletest now follows the "Abseil Live at HEAD" philosophy, which means
they recommend using the latest commit on the master branch and always
compiling from source. They recommend this to avoid version mismatch
issues and "diamond dependency" problems which are common in dependency
graphs with pinned versions. Google make the "promise" that future
changes won't break downstream code if it follows the "Abseil
compatability guidelines".

Upping the version to master also fixes some CMake configure time
warnings that were present with the older tagged releases of googletest:

CMake Deprecation Warning at __build/_deps/googletest-src/CMakeLists.txt:4 (cmake_minimum_required):
  Compatibility with CMake < 2.8.12 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

CMake Deprecation Warning at __build/_deps/googletest-src/googlemock/CMakeLists.txt:45 (cmake_minimum_required):
  Compatibility with CMake < 2.8.12 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

CMake Deprecation Warning at __build/_deps/googletest-src/googletest/CMakeLists.txt:56 (cmake_minimum_required):
  Compatibility with CMake < 2.8.12 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

CMake: unit-tests: Remove trailing whitespace from stubs/CMakeLists.txt

CMake: unit-tests: Remove trailing whitespace

CMake: Remove trailing whitespace from CMakeLists.txt

mbedtls: Rename Mbed timing implementation ...

We get a linker warning with the recently added timing module
implementation for Mbed. This is because there is Mbed TLS also ships a
file called timing.c, which we are including in Mbed OS also. With CLI
1, we get an error about unique object files because of the similarly
named implementation files.

    Object file timing.o is not unique! It could be made from: mbed-os/connectivity/mbedtls/source/timing.c mbed-os/connectivity/mbedtls/platform/src/timing.cpp

Rename the Mbed timing module implementation to timing_mbed.cpp to avoid
this naming conflict.

Fixes: b8781e527bc1 ("mbedtls: Add an alt implementation of timing")

Fixes #14759

Merge pull request #14746 from jeromecoutant/PR_WB15CC ...

STM32WB: introduce STM32WB15CC NUCLEO

Merge pull request #14659 from arduino/i2c_slave_patch ...

STM32: make i2c_salve_read return the number of bytes read

fix typos ...

Co-authored-by: Chris Swinchatt <christopher.swinchatt@arm.com>

Merge pull request #14756 from Patater/tls-timing-alt ...

mbedtls: Add an alt implementation of timing

mbedtls: Add an alt implementation of timing ...

Implement the MBEDTLS_TIMING_ALT interface for Mbed OS. This
implementation is sufficient to run the Mbed TLS benchmarking
application.

Merge pull request #14713 from Patater/lgtm ...

lgtm: Add initial LGTM configuration file

Merge pull request #14740 from chrisswinchatt-arm/fix-netsocket-dynalloc ...

Fix 'netsocket: several dynamic allocation results not checked' (#14210)

add_event_listener in NetworkInterface now returns an error if the method fails. Previous attempts to add the event listener would attempt to use an unchecked standard dynamically allocated ns_list_* item.

In other cases, the dynamically allocated items will now be checked, and if unsuccessful, will return after cleaning up any outstanding issues.

TCPSocket::accept will now check that its own internally allocated new TCPSocket call will succeed, and if not, will clean up the stack resources. This should help when memory is low but an incoming connection requests a connection when the TCPSocket is listening.

Merge pull request #14704 from jeromecoutant/PR_TEST_PIN ...

Pin name tests update